Pneumatic tool lubricant

ABSTRACT

A PNEUMATIC TOOL LUBRICANT COMPRISING A MAJOR AMOUNT OF HYDROCARBON LUBRICATING OIL AND MINOR AMOUNTS OF MOLYBDENUM DISULFIDE, ZINC DIALKYLDITHIOPHOSPHATE, ORGANIC SULFUR COMPOUND COMPOSED ONLY OF CARBON, HYDROGEN, SULFUR, AND OXYGEN, AND A RUST INHIBITOR SELECTED FROM THE GROUP CONSISTING OF ALIPHATIC MONOCARBOXYLIC ACIDS, SULFONIC ACIDS, AND METAL SALTS THEREOF.

United States Patt ce 3,801,503 Patented Apr. 2, 1974 ABSTRACT OF THEDISCLOSURE A pneumatic tool lubricant comprising a major amount ofhydrocarbon lubricating oil and minor amounts of molybdenum disulfide,zinc dialkyldithiophosphate, organic sulfur compound composed only ofcarbon, hydrogen, sulfur, and oxygen, and a rust inhibitor selected fromthe group consisting of aliphatic monocarboxylic acids, sulfonic acids,and metal salts thereof.

BACKGROUND OF THE INVENTION Field of the invention This inventionrelates to pneumatic tools and similar apparatus.

Pneumatic tools, usually compressed air-driven, are quite common andwidely used. The largest group of pneumatic tools consists of those thatare operated by one man and are either handheld or mounted on a smallmovable carriage. Typical examples of this kind of tool are thejackhammer, rock drill, and pneumatic wrench.

Because of the severe impact operating conditions of pneumatic tools,lubricants for such tools have been formulated to attempt to meetdemands not required of lubricants for other services. The pneumatictool lubricants should lubricate the pneumatic tools without beingsubstantially affected by the presence of large amounts of dust andwater, and they should also serve to keep the dust and water out of theoperating parts of the tool. Since water vapor and often aqueous acidsare present in the compressed air supplied to the tool or in theimmediate vicinity of the work site, the lubricant should also protectthe tool from rusting and acid corrosion. In addition, the lubricantshould, of course, not itself adversely affect the tool.

Lubricants for pneumatic tools, particularly lubricants designed to beused in the hot and poorly ventilated confines of mines, should alsohave properties not ordinarily required of lubricants. First, thelubricant and its byproducts should not contribute significantly tofouling of the atmosphere in the vicinity of the tool. The lubricantshould also be capable of being injected into the air supply line to theair-driven tool and carried from the remote supply point to thelubrication points of the tool. Finally, the lubricant should minimizethe occurrence of dieseling. This is an explosion phenomenon similar tothe compression ignition that occurs in a diesel engine and is caused inpneumatic tools by the oil/air mixture exploding in the compressionchamber of the air-driven tool.

Prior art lubricants, however, have all failed to meet one or more ofthese stringent demands. Users of pneumatic tools have experienced highbreakdown rates of their tools, requiring frequent and costly overheaulsand cutting production by removing needed tools from service, and havebeen plagued by the problems of dieseling, rusting, and stray misting.

Description of the prior art A pneumatic tool lubricant containing asulfurized fatty oil is described in US. Pat. 2,734,868. The use ofmolybdenum disulfide as a compound of a lubricating oil is disclosed ina large number of patents, among them US.

Pats. 2,156,803 and 3,078, 227. The other components of the claimedlubricant are also individually described in the art. A lubricantcontaining mixed base oil, zinc dialkyldithiophosphate, and a sulfurizedfatty oil has been sold commercially for use in pneumatic tools.

SUMMARY I have now invented a lubricant composition which successfullymeets all the stringent requirements described above and which providesthe effective lubrication of pneumatic tools which has been heretoforeunobtainable.

This lubricant composition is-prepared by combining 9.

major portion of an viscosity index hydrocarbon lubricating oil andminor effective amounts each of (1) molybdenum disulfide, (2) an organicsource of sulfur providing the composition with at least 0.5 weightpercent sulfur, (3) a zinc dialkyldithiophosphate, and (4) an organicpolar-nonpolar rust inhibitor.

DETAILED DESCRIPTION OF THE INVENTION The lubricant of this invention isformulated to provide long-term lubrication to pneumatic tools whilereducing the occurrence of dieseling, stray misting, and rusting. Infield tests, the lubricant has been shown to extend service life of rockdrills between overhauls by factor of seven or more, while reducingdieseling, rusting, and stray misting to insignificant levels.

The lubricant of this invention will have a viscosity index of 80 orhigher, and in the multigrade forms defined below the viscosity indexmay be as high as 140-150. Viscosities at F. may range from 100 to2,200, depending on the grade desired; excellent service has beenobtained with lubricants having viscosities in the range of 3001,000 SUSat 100 F. The lubricant will contain approximately 0.17-0.25 weightpercent zinc, 0.831.0 Weight percent organic sulfur, and O.18-0.25weight percent phosphorus. It also contains molybdenum, which isincorporated from the M08 described below. The lubricant has a fiashpoint of at least 300" F. and a pour point dependent on the viscosityand viscosity index.

The lubricant of this invention is produced by blending together a majorportion of a hydrocarbon lubricating oil having a natural viscosityindex of at least 80 and (1) 0.001 to 15.0 parts by weight of molybdenumdisulfide, (2) 0.5-10.0 parts by weight of an organic source of sulfurproviding the total composition with a sulfur content of at least 0.5weight perecnt, (3) 0.1 to 5.0 parts by weight of a zincdialkyldithiophosphate, and (4) 0.1 to 4.0 parts by weight of an organicpolar-nonpolar rust inhibitor. In narrower embodiments which will bediscussed below, the lubricant may also contain additives such as anoiliness agent, a tackiness agent, a colorant, a viscosity indeximprover, etc.

One component of the blend is molybdenum disulfide, a mineral whichresembles graphite in appearance. In the compositions of this invention,the molybdenum disulfide is used in a finely divided form and isdispersed throughout the lubricating oil. The molybdenum disulfide (MoSwill be present in the amount of 0.00115.0 parts by weight. (Allcontents herein are by weight, and all are measured on the basis of thetotal lubricant composition, as though each component wholly retainedits individual identity. The actual form in which the materials existafter blending is as a complex mixture of initial components andreaction products, whose exact composition is unknown.) The preferredconcentration is l02,000 p.p.m. M05 The particles of molybdenumdisulfide will have diameters in the range of one to 5 microns andnormally will not exceed three microns in diameter. Finely dividedmolybdenum disulfide is commercially available and is generally sold asconcentrations of molybdenum disulfide particles suspended in diluentoil. These may be blended directly with the other materials to form thecompositions of this invention when the diluent oils are notincompatible with the other components of the composition.

The blend will also include an organic source of sulfur containingsufiicient sulfur to provide the finished lubricant with a sulfurcontent of at least 0.5 weight percent. The organic source of sulfurwill be present as 05-1020, preferably 1.5-6.0, parts by weight of thecomposition.

Organic source of sulfur, as used herein, refers to compounds ormixtures of compounds containing only carbon, hydrogen, oxygen, andsulfur. The oxygen present will be in the form of ether linkages or incarbonyl, carboxylate, or hydroxyl groups. Each sulfur atom will have atleast one bond to a carbon atom or to another sulfur atom. The number ofsulfur atoms in the organic source of sulfur will average in the rangeof 2-20, preferably 2-8, per molecule. The number of carbon atoms willaverage in the range of -70 per molecule. The compounds will normallyhave molecular weights not exceeding about 1,000 and preferably notexceeding 700. It is preferred that the compounds be selected from thegroup consisting of aliphatic polysulfides, sulfurized fatty oils andmore preferably, mixtures of these two materials. Aliphatic polysulfideas used herein refers to a mixture of compounds each of which consistsof two monovalent alkyl radicals and on the average of 2 to 8,preferably 3 to 6, sulfur atoms. The alkyl radicals are linked throughone or more sulfur atoms. All sulfur atoms except the one or two bondedto the alkyl groups will be bonded only to other sulfur atoms. The alkylradicals may be the same or different and are of from 1 to 30 carbonatoms, preferably 10 to 25 carbon atoms. The total number of carbonatoms in each compound must equal 10 to 60. It is preferred that thealkyl radicals be alike; i.e., that the compounds be dialkylpolysulfides. Representative aliphatic polysulfide structures areillustrated in U.S. Pats. 2,153,- 973; 2,237,526; 2,398,415; and3,013,969.

Typical aliphatic poly-sulfides which may be used include didodecylpolysulfide, dieicosyl polysulfide, dipentacosyl polysulfide,dodecylheptadecyl polysulfide, mixtures of polysulfides produced bysulfurizing mixed C -C olefins derived from cracked wax, etc. Typicalsulfurized fatty oils which are useful in this composition includesulfurized lard oil, sulfurized sperm oil, sulfurized fish oil,sulfurized palm oil, sulfurized peanut oil, sulfurized corn oil,sulfurized cottonseed oil, sulfurized rosin oil, sulfurized tall oil,etc.

Also included in the blend is a zinc dialkyldithiophosphate. These arewell-known compounds widely described in the prior art. The alkylcomponents may be straightor branched-chain, and will generally eachhave 4-18, preferably 4-12, carbon atoms. They may be the same ordifferent.

The zinc dialkyldithiophosphate will be present as 0.1-5.0, preferably0.l-2.0 part by weight of the composition. Typical compounds which maybe used include the zinc salts of the reaction products of P 8 and anyone or two alcohols such as sec.-butyl alcohol, 4-methyl- 2-pentanol,l-butanol, l-hexanol, 2-butanol, 3-ethyl-1- hexanol, l-octanol,l-dodecanol, etc. The alcohols are normally primary and secondaryalcohols.

Another component of the blend will be an organic polar-nonpolar rustinhibitor. This may be a single type of material which itself has rustinhibiting properties, or, more usually, it will be a synergisticmixture of about two or three components which together provide rust andcorrosion inhibition. Organic polar-nonpolar rust inhibitors aredescribed in detail by Zisman et al. in Advances in Petroleum Chemistryand Refining, vol. 2, (Interscience Publ., Inc. 1959) beginning on page94. Typical of these rust inhibitors are high molecular weight organicacids such as naphthenic, oleic, and sulfonic acids; salts of theseacids, such as neutral and overbased petroleum and mahogany sulfonatesof alkali and alkaline earth metals, especially calcium and barium; andthe neutralized products of the reaction of these acids and organicbases such as substituted amines. Preferred in this invention are thesulfonate salts, and more preferably the alkaline earth metal petroleumsulfonates, especially the neutral calcium salt. If desired, the neutralcalcium salt may be combined with 0.001 to 0.02 part by weight per partby weight of total rust inhibitor of synergistic enhancing materials,such as a polyalkylene glycol of 1,800-2,300 number average molecularweight and a polyalkylene glycol alkyl ether of 95 0-1,150 numberaverage molecular weight. The organic polar-non-polar rust inhibitorwill be present in 01-40 parts by weight preferably 0.5-1.5 parts byweight of the composition.

The major portion of the lubricant of this composition consists of ahydrocarbon lubricating oil. This oil will be present as 65-95 parts byweight of the lubricant composition, preferably as -95 parts by weight.It is preferred that the oil be paraflinic. This is a general definitionwhich normally refers to the type of crude oil from which thelubricating oil' has been derived, and differentiates the oil from thosederived from mixed base and naphthenic crude oils. The definitions ofthese oils do not involve specific composition limits; rather, they arebased on a number of factors and properties which are believed tocharacterize different types of oils. These are discussed in Nelson,Petroleum Refinery Engineering (4th ed., McGrawHill Book Co., Inc.,1958), beginning on page 80.

The oil must have a high natural viscosity index, i.e., of at least 80.It will generally be found that those oils which have the high naturalviscosity index are parafiinic oils. The oil may also be selected on thebasis of natural viscosity index to provide an inherent minimization ofthe effects of wide fluctuations in ambient temperature. (This ability,which is analogous to the multigrade properties of automotive oils asdefined by Society of Automotive Engineers standards, will be referredto herein as multigrade capability and the oils with this ability asmultigrade oils for convenience, even though there are no comparableofficial standards for industrial oils.)

In certain services, it will be advantageous to include a small amountof a detergent-dispersant in the lubricant composition; i.e., on theorder of 025-10 part by weight. Typical detergent-dispersants which aresuitable for use in these lubricants include the alkyl-substitutedsuccinimides of the type described in US. Pat. 3,202,678; petroleumsulfonates; alkyl phenates; polar/nonpolar polymers such asalkylmethacrylate/vinylpyridine copolymers,alkylmethacrylate/polyalkylene glycol methacrylate copolymers; etc.

Another additive which may be present in the composition is a metaldeactivator. Bronze is often used for various parts of pneumatic tools,and is quite susceptible to corrosion by certain components oflubricants. A metal deactivator prevents corrosion of the bronze byforming an inert film on the metal and preventing its contact with thecorrosive lubricant components. Metal deactivators are generally presentin very small amounts; normally they will comprise only 0.01-0.05 partby weight, preferably about 0.02 part by weight of the composition.Typical of the metal deactivators which may be used is quinizarin. Thelubricant compositions may also contain tackiness or stringiness agentssuch as long-chain polymers, e.g., polybutene and polyethylene.Tackiness agents aid the lubricant in adhering to the metal surface tobe lubricated. Another type of optional additive is in an oilinessagent. These include fatty oils and acids and synthetic esters of fattyacids. If desired, one may select as the source of organic sulfur acompound or mixture of compounds which provides oiliness as well assulfur. The composition may also contain additives such as antifoamingagents, colorant, and other additives described in the art. The totalamount of these additives will generally not exceed 5.0 parts by weightof the composition, and will usually be in the range of about 1.0-3.0parts by weight.

When a lubricant with broader multi-grade capabilities than availablemerely by the choice of the lubricating oil base is desired, a viscosityindex improver may be added. A number of viscosity index improvers havebeen described in the art. In general, these are either isobutenepolymers or acrylate e.g. methacrylate polymers. Several satisfactorymaterials are commercially available under various trade names.Viscosity index improvers are generally used in concentrations of about30-150 parts by weight of the composition, generally about 4.010.0 partsby weight.

The lubricant compositions of this invention are normally producedsimply by mixing the various components together with the base oil. Thecomponents may be added to the base oil neat or may be present asconcentrations in diluent oils where the diluent oils are compatible andmiscible with the base oil. If desired, various groups of individualcomponents may be separately mixed, and these mixtures blended togetherto produce the finished lubricant. Mixing times may be from 1 minute to24 hours; the components are mixed until a homogeneous composition isobtained. Mixing can be done at room temperatures or at temperatures upto about 200 F.; use of elevated temperatures will often aid in thedispersion of the components.

The following examples will illustrate the compositions of thisinvention. Amounts of components are described in parts by weight.

EXAMPLE 1 A base oil having a viscosity index of 85 for a single gradepneumatic tool lubricant was formulated by blending 78 parts of aparaffinic neutral oil having a viscosity at 100 F. of about 480 SUS anda gravity of approximately 28.5 API with 15 parts of a paraffinic brightstock having a viscosity at 210 F. of 180 SUS and a maximum pour pointof 15 F. To this base oil were added 2 parts of an aliphatic polysulfideproduced from cracked wax olefins and containing approximately 17.5weight percent sulfur, 2 parts of zincdi(1-methylpropyl/1,3-dimethylbutyl) dithiophosphate containingapproximately 7 weight percent phosphorus and 15 weight percent sulfur,1 part of a mixture of 93 parts of a neutral calcium sulfonate and 0.7part each of polypropylene glycol and polypropylene glycol butyl ether,0.5 part of a molybdenum disulfide dispersion commercially availableunder the trade name Molykote M, and 0.3 part of a high molecular weightpolyisobutene commercially available under the trade name Paratac. Tothis mixture were added 2 parts of a blend of sulfurized lard oil andquinizarin in a ratio of 50:1. A minor amount of an antifoaming agentwas also added. The resulting pneumatic tool lubricant composition wasfound to have a viscosity at 100 F. of 656 SUS and a viscosity index of95.

This lubricant was used in a field test in various pneumatic tools,including rock drills, operated in a hard rock copper mine in Arizona.In previous service using a commercial pneumatic tool oil, the rockdrills had operated for an average of approximately 1-10 days before thecombined effects of overheating, dieseling, and waterwashing of thelubricant required overhauls, With the lubricant of this example,however, the average time between overhauls was extended toapproximately 2-3 months of operation. By using the oil of thisinvention, oil feed rate was decreased by up to 50 percent with nosticking or binding of the rock drills. Oil fog or mist in the vicinityof the drill, smoking, and dieseling were all substantially eliminated.No rusting of the tools was observed over an extended period.

EXAMPLE 2 A base oil having a viscosity index of 96 for a multigradepneumatic tool lubricant was prepared by blending 61 parts of aparaffiuic neutral oil having a viscosity at F. of a SUS and a gravityof approximately 31.2 API with 20 parts of the neutral oil described inExample 1, and 2 parts of the bright stock described in Example 1. Tothis mixture were added 10 parts of a polyisobutene viscosity indeximprover commercially available under the trade name Paratone N and thecomponents described in Example 1 in the same amounts as stated above.This lubricant composition had a viscosity at 100 F. of 447 SUS and aviscosity index of 145. In field tests in the same mine, this lubricantwas found to have the same high performance qualities as the singlegrade lubricant described in Example 1.

It is apparent from these data that the pneumatic tool lubricants ofthis invention have superior lubricating properties, in the extremelysevere service environments common to hard rock mining tools. Theyprovide substantially increased tool life, accompanied by a reducedfouling of the atmosphere in the vicinity of the operating tool. Theformer property substantially improves the economics of mining, for thereplacement and overhaul cost of tools is substantially reduced. Thelatter property reduces the health hazards faced by miners working withor in the vicinity of pneumatic tools.

The above examples are meant for illustrative purposes only. It isapparent that many embodiments of this invention may be compoundedwithout departing from the scope and spirit of the invention.

I claim:

1. A lubricant composition for pneumatic tools which is formulated bycombining 65 95 parts by weight of a hydrocarbon lubricating oil havinga viscosity index of at least 80 and (1) 0.001 to 15.0 parts by weightof molybdenum disulfide; (2) 0.5 to 10.0 parts by weight of an organicsource of sulfur containing only carbon, hydrogen, sulfur and oxygen;wherein each of said sulfur atoms is bonded to carbon or at least oneother sulfur atom, and said oxygen is present only in the form of etherlinkages or carbonyl, carboxylate, or hydroxyl groups; and capable ofproviding said lubricant composition with a sulfur content of at least0.5 weight percent; (3) 0.1 to 5.0 parts by weight of a zinc di(C -Calkyl) dithiophosphate; and (4) 0.1 to 4.0 parts by weight of an organicrust inhibitor selected from the group consisting of aliphaticmonocarboxylic acids, sulfonic acids, and metal salts thereof.

2. The composition of claim 1 wherein said molybdenum disulfide ispresent as 10 to 2,000 ppm. of said composition.

3. The composition of claim 1 wherein said organic source of sulfur isselected from the group consisting of aliphatic polysulfide, sulfurizedfatty oil, and mixtures thereof.

4. The composition of claim 1 wherein said zinc di- (C C alkyl)dithiophosphate is a zinc di(C -C alkyl) dithiophosphate.

5. The composition of claim 1 wherein said organic rust inhibitorcomprises a neutral alkaline earth metal salt of a petroleum sulfonicacid. I

6. The composition of claim 1 wherein said hydrocarbon lubricating oilis a paraffinic oil.

7. The composition of claim 1 formulated by combining the materials ofclaim 1 and 3.0 to 15 .0 parts by weight of a viscosity index improverselected from the group consisting of acrylate polymers and isobutenepolymers.

8. The composition of claim 1 formulated by combining 8095 parts byweight of a parafiinic hydrocarbon oil having a viscosity index of atleast 80, and (1) 10 to 2,000 p.-p.m. of molybdenum disulfide; (2) 1.5to 6.0 parts by weight of an organic source of sulfur selected from thegroup consisting of aliphatic polysulfide, sulfurized fatty oil, andmixtures thereof; (3) 0.1-20 parts by weight of a zinc di(C C alkyl)dithiophosphate, and (4) 0.5 to 1.5 parts by weight of an organic rustinhibitor selected from the group conslsting of neutral calciumpetroleum References Cited sulfonate and neutral barium petroleumsulfonate.

9. The composition of claim 8 formulated by combin- UNITED STATESPATENTS ing the materials of claim 8 and 4.0 to 10.0 parts by weight3,442,804 5/1969 Le Suer et aL of a viscosity index improver selectedfrom the group con- 5 3,078,227 2/1963 Zaunelet a1. 252 25 sisting ofacrylate polymers and isobutene polymers. 3,281,355 10/1966 c h et 1252;. 25

10. A process for lubricating a pneumatic tool which comprises applyingto a lubrication point of said tool the DANIEL WYMAN, Primary Examinercomposition of claim 10 I. VAUGHN, Assistant Examiner 11. A process forlubrlcatmg a pneumatic tool WhlCh comprises applying to a lubricationpoint of said tool the US. Cl. X.R. composition of claim 8. 5 5 389

